1. Field of the Invention
This invention relates to a heating device in conjunction with an inhalation therapy device, and more particularly, to an electric heating device for heating an aerosol spray produced by a disposable nebulizer.
2. Prior Art
A number of respiratory ailments are treated by having the patient inhale an aerosol spray of finely divided particles of water or other liquid medicaments. Devices referred generally as nebulizer devices have evolved which are designed to produce such an aerosol spray. Nebulizers introduce a stream of pressurized gas, usually oxygen, into a chamber which entrains liquid particles so as to form the spray. Examples of these devices are shown in U.S. Pat. Nos. 3,652,015; 3,836,079; 3,915,386; and 4,036,919.
In order to prevent cross-contamination, it is generally preferred that a nebulizer be manufactured as a single use disposable device. In addition, the water supply which is used to form the aerosol is usually provided in a prefilled disposable bottle which is connected to the nebulizer. Since both the nebulizer and water supply bottle are disposable, their manufacturing cost must be kept low.
It has been determined that it is beneficial to the patient if the aerosol spray which is delivered is at or near body temperature. Since the water supply is generally at room temperature or below and some cooling occurs in the nebulization process, some type of external heating device is generally required. Most prior art heating devices are immersion type heaters which are placed directly in the water supply bottle and heat the entire water supply. As these heaters directly contact the water which will ultimately be delivered to the patient, the must be sterilized before each use. Systems which heat only a small portion of the water supply, just prior to nebulization, are shown in U.S. Pat. Nos. 3,903,833; 4,036,919; 3,864,544; 4,012,473; and 4,084,587. These devices, while providing improved performance over immersion type heaters, have certain drawbacks with respect to complexity or otherwise which has limited their acceptance.
It is a primary object of the present invention to provide a heater for use with a nebulizer which can be re-used, is easily attached and removed from the nebulizer and has no adverse effects upon the sterility of the nebulizer system.
Although all nebulizers appear to heat the water supply before the aerosol is formed, it is known to provide a means for heating liquid particles after they have been suspended in a gas, as is shown in U.S. Pat. Nos. 4,051,205 and 4,060,576. These patents are directed to humidifier systems which include a humidifier having a bottom humidification chamber containing a predetermined amount of liquid. The humidifier rests upon a "hot plate" type heater which heats the liquid in the humidification chamber, causing gas passing through the chamber to become humidified. The humidified gas is passed through a delivery hose which includes an integral heater. The use of a delivery hose with an integral heater presents sterilization and cost problems should re-use of the delivery hose be required. In addition, the hose is specifically designed to be used in conjunction with a humidified gas which has already been heated, as opposed to an unheated aerosol formed in a nebulizer. Furthermore, it is believed that the heating of the wet gas destroys aerosol mist particles and this would not be suitable for use with a nebulizer. It is a further object of the present invention to provide a nebulizer system in which all heating is accomplished within the nebulizer and which heats the aerosol spray formed in the nebulizer rather than the water supply which is used to create the aerosol.